Path: news.cs.au.dk!not-for-mail
From: Flemming Gram Christensen <gram@ull.mjolner.dk>
Newsgroups: comp.lang.beta
Subject: Re: How to copy a bitmap object (nti)?
Date: 10 Feb 2000 15:49:09 +0100
Organization: University of Aarhus, Department of Computer Science (DAIMI)
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"Sascha Kimmel \(tricos Mediaservice\)" <kimmel@tricos.com> writes:

> Hi!
Hi.

I think you can do
a pixmap.init to get a fresh bitmap.
Then use pixmap.drawpixmap to draw the background on this.
then pixmap.drawpixmap again to draw the sprite on top.

Regards
/gram
> 
> I want to copy a bitmap object (on Windows) to realize a simple image buffer
> for animation.
> (See http://msdn.microsoft.com/library/techart/msdn_anim32.htm and
> http://msdn.microsoft.com/library/techart/msdn_flicker.htm for details)
> This works as follows: you have a bitmap which is the background, a sprite
> (also a bitmap) that you draw onto the background bitmap - and then copy the
> resulting bitmap to the screen - this prevents flickering ("single buffer").
> 
> So I need to copy a bitmap (pixmap in beta):
> 
> ...
> screenBitmap,bg,sprite,buffer:^pixmap;
> do
> (** INIT **)
> &pixmap[]->buffer[];
> &pixmap[]->screenBitmap[];
> 'background.bmp'->screenBitmap.read;
> &pixmap[]->bg[];
> 'background.bmp'->bg.read;
> &pixmap[]->sprite[];
> 'sprite.bmp'->sprite.read;
> 
> ...
> 
> (** Off-screen drawing **)
> bg[]->buffer[]; (** well, here's the problem !! **)
> (sprite[],(0,0),(5,5),sprite.width,sprite.height)->buffer.drawPixmap;
> 
> 
> (** Copying buffer to screen bitmap **)
> buffer[]->ScreenBitmap[]; (** another problem **)
> ...
> 
> 
> Due to the use of references instead of objects (a->b, (a,b pixmaps) gives a
> compiler error) when assigning bg[] to the buffer[] and the following
> drawPixmap both buffer[] and bg[] point to the same pixmap, so *both* are
> changed.
> 
> Any solution?
> 
> Regards,
> Sascha Kimmel
> 
> 

-- 
/Flemming Gram Christensen

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